1. Field of the Invention
The present invention relates to an ignition system for an automobile engine.
2. Description of the Prior Art
A conventional multi-ignition system supplies ignition currents to the ignition plug many times in a certain period of time in which responds to an ignition timing signal. This prevents the ignition from misfire and knocking by applying a high voltage power many times. This kind of multi-ignition system uses an ignition condenser placed between the power supply and the ignition coil. The condenser supplies a power energy to the ignition coil. FIG. 4 is a circuit diagram of an ignition system shown in Japanese Patent Laid-Open Hei 1-116281 (1989). Referring to FIG. 4, an engine computer CPU sends an ignition timing signal out to a control circuit 112. A oscillator 206 turns on and off the charge circuit 100 in response to an ignition timing signal to charge an ignition condenser 101. The oscillator 206 also controls a transistor 107 to discharge the condenser 101 through an ignition coil 102. This discharge energy of the ignition coil 102 provides the energy to spark the plug 103. When the condenser 101 discharges, the discharge current from the condenser 101 through the choke coil 128 and the coil 102 increases in accordance with a frequency of the circuit. The discharge current becomes the maximum when a charge of the condenser 101 becomes zero. At the same time a magnetic energy stored in the coil 102 and the choke coil 128 also becomes the maximum. This magnetic energy turns on the first diode of the second current circuit 110 to keep supplying the ignition energy to the ignition plug. The primary current of the coil 102 decreases as the ignition plug 103 consumes the ignition energy. When the primary current becomes too low to supply the ignition energy to the ignition plug 103, the transistor 107 turns off. The Zener diode 129 of the first current circuit 205 turns on to draw the current of the primary coil of the coil 102. Thus the energy in the coil 102 discharges through the first current circuit 205. The charge and discharge of the condenser 101 which provides the plug with the ignition energy repeats many times in one ignition timing signal.
This type of the ignition system can provide a higher energy by the condenser which repeats a charge and a discharge repeatedly. The system, however, requires a time to charge the condenser during the ignition timing. Spark break which is a time period between two sparks is a fairly long time of period because of a charging time of the condenser.
A spark of the plug may not be sufficient to burn the fuel continuously and causes a misfire. If a misfire occurs during a time of charging a condenser, the fuel remains unburnt until the plug sparks in a next time. This may result a higher tail pipe emission and a lower driving ability.